ACE-031 (also called Ramatercept) is a research protein made by fusing part of a human muscle-growth receptor (ActRIIB) to an antibody fragment (IgG1-Fc). It acts as a soluble decoy that intercepts molecules like myostatin, which normally limit muscle growth. It is not an approved medicine and is for research use only.[5]

How does ACE-031 work?

ACE-031 works by binding to and neutralizing proteins — especially myostatin and activin A — that tell your body to suppress muscle growth. By acting as a molecular sponge for these inhibitory signals, it allows muscle-building pathways to operate with less interference. It targets multiple negative regulators simultaneously, which is why researchers consider it a broad-acting approach.[4][5]

What is ACE-031 used for in research?

Researchers have studied ACE-031 primarily for muscle-wasting conditions. Clinical trials explored its use in Duchenne muscular dystrophy and in healthy postmenopausal women as a model for age-related muscle loss.[3][5] Non-human primate studies extended those findings to marmosets, showing gains in lean mass and muscle force.[4] Anti-doping scientists also study it to develop detection methods.[1]

How is ACE-031 dosed in research?

Research doses have ranged widely depending on the study model and goal — from very low single doses in early human safety trials to repeated dosing in disease models. Specific milligram figures for each published study are laid out in the dosage chart on this page. These are research reference figures only and do not constitute medical advice or guidance for human use.[5][3]

How do you reconstitute ACE-031?

As a freeze-dried protein, ACE-031 is typically reconstituted in research settings by slowly adding sterile bacteriostatic water to the vial, then gently swirling — never shaking — to dissolve the powder. The resulting solution should be refrigerated at 2–8 °C and used within the timeframe specified by the research protocol. Repeated freeze-thaw cycles degrade the protein and should be avoided.

Based on available clinical research, ACE-031 showed a generally tolerable profile in a single-dose human study, with injection-site redness as the main side effect.[5] However, a DMD trial was halted early due to non-muscle-related concerns including nosebleeds and small blood vessel changes.[3] ACE-031 is not approved for human use. Black-market products claiming to be ACE-031 have been found to contain impurities and incorrect proteins.[1]

ACE-031 10mg Vial Dosage Protocol

Reconstitution and dosing for a 10mg vial of ACE-031 — concentration by BAC-water volume, the units to draw on a U-100 syringe, and the cited dosing chart.

Goal	Dose	Frequency	Duration	Evidence	Source
Single ascending dose safety/PK/PD in healthy postmenopausal women	0.02–3 mg	single dose	per trial	Clinical	PMID 23169607
Muscle mass increase (statistically significant lean mass and thigh volume) in healthy postmenopausal women	3 mg	single dose	per trial	Clinical	PMID 23169607
Safety/PD evaluation in ambulatory boys with Duchenne muscular dystrophy	0.02–3 mg	1x/2-4 weeks	per trial	Clinical	PMID 27462804
Skeletal muscle growth (preclinical mouse model)	10 mg	per trial protocol	28 days	Preclinical	PMID 20466801
Suboccipital muscle hyperplasia model / intracranial pressure study in rats	10 mg	per trial protocol	16 weeks	Preclinical	PMID 36054096
Black market product detection study in rats	10 mg	single dose	per trial	Preclinical	PMID 40312924

BAC water	Concentration	Volume / dose	Units (U-100)
1 mL	10 mg/mL	0–0.3 mL	0.2–30
2 mL	5 mg/mL	0–0.6 mL	0.4–60
3 mL	3.33 mg/mL	0.01–0.9 mL	0.6–90

What is ACE-031?

ACE-031 — also called Ramatercept — is a research protein, not a small drug molecule. Scientists built it by fusing a piece of a human cell receptor (called activin receptor type IIB, or ActRIIB) to a section of a common antibody protein (IgG1-Fc). The result is a soluble "decoy" receptor that floats freely in the bloodstream.^[5] It has never been approved as a medicine, and it remains strictly a research compound. It is also banned in sport by WADA.^[1]

How ACE-031 Works

Think of muscle growth like a thermostat. Your body keeps muscle size in check using proteins called myostatin and activin A — these are the "turn it down" signals. ACE-031 acts like a sponge that soaks up those signals before they can reach muscle cells. With fewer "turn it down" messages getting through, muscle-building processes can run more freely.^[5] Because it traps multiple negative regulators at once, ACE-031 is thought to have a broader effect than blocking just one signal in isolation.^[4]

What the Research Shows

Studies in Humans

The first human trial tested a single dose in 48 healthy postmenopausal women across a range of doses. At the highest dose studied, researchers measured a statistically significant 3.3% increase in total lean body mass and a 5.1% increase in thigh muscle volume by day 29, both confirmed by imaging. The drug also appeared to influence bone and fat metabolism markers. It was generally well tolerated, with injection-site redness being the most common side effect.^[5]

A separate randomized, placebo-controlled trial enrolled ambulatory boys with Duchenne muscular dystrophy (DMD) — a progressive muscle-wasting disease — and gave ACE-031 subcutaneously every 2–4 weeks. The primary goal was safety evaluation. No serious or severe adverse events were linked to the drug, but the trial was stopped early after researchers noticed non-muscle-related findings including nosebleeds and small visible blood vessel changes (telangiectasias). Researchers observed trends — not statistically significant — toward preserved walking distance, increased lean mass, and improved bone density compared to placebo.^[3] The compound was listed as entering early clinical evaluation as far back as 2010.^[6]

Studies in Non-Human Primates

A study in common marmosets (small primates) found that ACE-031 produced a significant increase in lean body mass and body weight over 14 weeks. Muscle fiber cross-sectional area grew in both slow-twitch (type I) and fast-twitch (type II) fibers of the biceps. Muscle force production also improved in laboratory testing. Researchers concluded that success in a non-human primate raises the plausibility of benefit in human muscle diseases.^[4]^[2]

Detection and Black-Market Product Concerns

Because ACE-031 is prohibited in competitive sport, anti-doping laboratories have developed methods to detect it. A 2025 study tested 14 black-market products claiming to be ACE-031. Only 12 contained any relevant protein at all, and those 12 appeared to contain the full-length receptor protein rather than the actual ACE-031 fusion protein — meaning the products were not what they claimed to be. Researchers used rats to test detection windows and found the substance detectable in blood for up to 48 hours after administration at the protocol dose.^[1] This finding underlines serious purity and identity concerns with unregulated market products.

What ACE-031 Is Being Studied For

Muscle-wasting diseases — including Duchenne muscular dystrophy and other myopathies^[3]
Age-related muscle loss — early human work focused on postmenopausal women^[5]
Bone and fat metabolism — biomarker changes suggest effects beyond muscle alone^[5]
Non-human primate models — to bridge the gap between mouse data and potential human application^[4]
Anti-doping science — developing reliable tests for illicit use^[1]

How ACE-031 Is Dosed in Research

Dosing has varied considerably across research contexts — from very small single doses to repeated administrations over weeks. The protocols span human clinical trials, animal disease models, and detection studies. Rather than reproduce every number here, refer to the dosage chart on this page for a clear, organized breakdown of each study protocol. If you need help scaling or converting a protocol figure, the calculator on this page can assist with the math. All figures in the chart are drawn directly from published research and are provided for reference and educational purposes only — not as guidance for human use.

Mixing and Storing ACE-031

ACE-031 is a protein, which means it is fragile compared to simple chemical drugs. In research settings, lyophilized (freeze-dried) protein powders like this are typically reconstituted by adding sterile bacteriostatic water slowly down the side of the vial — never shaken, only gently swirled — to avoid denaturing (unfolding and breaking) the protein structure. Once dissolved, the solution is generally kept refrigerated at 2–8 °C and used within a short window, often a few weeks, depending on the specific formulation and storage conditions stated by the supplier. Freezing reconstituted solution and thawing it repeatedly degrades protein quality. Always follow the specific reconstitution protocol provided with any research-grade material, and note that black-market products have been shown to contain impurities and incorrect proteins.^[1]

Sources

Gel Electrophoretic Detection of Black Market ACE-031. — Drug testing and analysis, 2025. PMID 40312924.
ACE-031, a Soluble Activin Type IIB Receptor, Increases Muscle Mass and Strength in the Common Marmoset (Callithrix jacchus). — bioRxiv : the preprint server for biology, 2025. PMID 41256654.
Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial. — Muscle & nerve, 2017. PMID 27462804.
ACE-031, a soluble activin type IIB receptor, increases muscle mass and strength in the common marmoset (Callithrix jacchus). — PloS one, 2026. PMID 41686840.
A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers. — Muscle & nerve, 2013. PMID 23169607.
Gateways to clinical trials. — Methods and findings in experimental and clinical pharmacology, 2010. PMID 20383346.

Storage & handling

Lyophilized (freeze-dried) peptide is typically kept refrigerated and protected from light; once reconstituted with bacteriostatic water it is generally refrigerated at 2–8 °C and used within a few weeks. Follow aseptic technique to avoid contamination, per CDC injection-safety guidance.

Injection technique

Subcutaneous injections are usually given into the fat of the abdomen or thigh: clean the site with an alcohol swab, pinch the skin, insert at the recommended angle, and rotate sites to protect the tissue. See MedlinePlus for a step-by-step subcutaneous-injection guide.

General aseptic-technique and injection references for educational use — they are not specific to any research compound.